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<p><img src="1714996872020.png" alt="1714996872020"></p>
<h2 id="指针变量"><a href="#指针变量" class="headerlink" title="指针变量"></a>指针变量</h2><figure class="highlight plaintext"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">指针变量用于保存变量的地址</span><br></pre></td></tr></table></figure>

<blockquote>
<ol>
<li>内存角度:指针变量、普通变量没有啥区别，都是一块内存，并且这块内存都有地址。唯一的区别：普通变量存储数据，指针变量存储地址</li>
</ol>
</blockquote>
<blockquote>
<ol start="2">
<li>语法角度: 指针变量多了个标识 <code>*</code>，以此表示这个变量中存储的是地址。</li>
</ol>
</blockquote>
<blockquote>
<ol start="3">
<li>普通变量有普通变量运算规则，指针变量有指针变量的运算规则。 如取值、赋值、加减运算</li>
</ol>
</blockquote>
<blockquote>
<ol start="4">
<li>指针无论什么类型、无论几级指针统统都是4个字节(32位) 8字节(64位)。因为他们存储的是一个内存地址，而内存地址大小是固定的。</li>
</ol>
</blockquote>
<blockquote>
<ol start="5">
<li>在相同平台上，无论什么类型的指针占用内存大小都是一样的。</li>
</ol>
</blockquote>
<blockquote>
<ol start="6">
<li>对指针变量取地址，才能拿到指针变量本身所占用的空间地址。如果直接使用指针变量，那么代表的是指针指向空间的地址。</li>
</ol>
</blockquote>
<h2 id="指针-操作符"><a href="#指针-操作符" class="headerlink" title="指针 操作符"></a>指针 操作符</h2><p><img src="https://file+.vscode-resource.vscode-cdn.net/Users/houyudong/Documents/Typora/blog/source/_posts/c%2B%2B/4%E3%80%81%E6%8C%87%E9%92%88%E5%92%8C%E5%87%BD%E6%95%B0%E6%8C%87%E9%92%88/1714997459927.png" alt="1714997459927"></p>
<blockquote>
<p><strong>&amp;</strong></p>
</blockquote>
<figure class="highlight plaintext"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br></pre></td><td class="code"><pre><span class="line">取地址符：取存储变量的内存地址</span><br><span class="line">int a =10;</span><br><span class="line">&amp;a; //获取a变量的地址，也就是10所在的内存块地址。对应上图中就是获取0x01地址。可对普通变量和指针变量使用</span><br></pre></td></tr></table></figure>

<blockquote>
<p><strong>*</strong></p>
</blockquote>
<figure class="highlight plaintext"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br></pre></td><td class="code"><pre><span class="line">取内容符：取地址中存放的数据</span><br><span class="line">int * num= &amp;a;</span><br><span class="line">*num //解引用，获取num所在的内存空间,也就是变量a的内存空间。</span><br><span class="line">*num=1 // 给0x01内存空间重新赋值为1</span><br><span class="line">---------------------------------</span><br><span class="line">当对一个指针变量num加*时，会先获取num的指针地址0x01，然后找到该地址对应的内存空间，在将1放到0x01这块内存中。如果int num2 = *num;则是取出num中存储的数据在赋值给num2.</span><br></pre></td></tr></table></figure>

<h2 id="指针声明"><a href="#指针声明" class="headerlink" title="指针声明"></a>指针声明</h2><figure class="highlight plaintext"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br></pre></td><td class="code"><pre><span class="line">指针变量声明的一般形式为： type * var_name = value;</span><br><span class="line">指针变量使用前一定要初始化，未出画的指针变量不能随便使用，否则会出现野指针。初始化时可以定义为空指针</span><br></pre></td></tr></table></figure>
<h3 id="野指针"><a href="#野指针" class="headerlink" title="野指针"></a>野指针</h3><figure class="highlight plaintext"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br></pre></td><td class="code"><pre><span class="line">指向非法的内存地址指针叫作野指针（Wild Pointer），也叫悬挂指针（Dangling Pointer），意为无法正常使用的指针。</span><br><span class="line"></span><br><span class="line">1、定义指针变量之后没有对它进行初始化,此时指针指向随机的内存地址，里面的内容不是我们想要的内容。</span><br><span class="line">2、指针指向某个对象之后，当这个对象的生命周期已经结束，对象已经消亡后，仍使用指针访问该对象，将出现运行时错误。</span><br><span class="line">3、指针释放后位置空。</span><br><span class="line"></span><br></pre></td></tr></table></figure>
<h3 id="空指针"><a href="#空指针" class="headerlink" title="空指针"></a>空指针</h3><figure class="highlight plaintext"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br></pre></td><td class="code"><pre><span class="line">空指针（Null Pointer）是一个不指向任何内存位置的指针。它存储段的基地址。空指针基本上存储了空值，而void是指针的类型。</span><br><span class="line"></span><br><span class="line">如果我们没有任何地址要分配给指针，那么它被称为空指针。当将NULL值赋给指针时，它被视为空指针。</span><br></pre></td></tr></table></figure>
<p><img src="1714997459927.png" alt="1714997459927"></p>
<figure class="highlight c++"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br></pre></td><td class="code"><pre><span class="line"> <span class="comment">//定义了一个普通int类型变量num，他的值为10.对应上图就是0x01内存块中存储的内容</span></span><br><span class="line"><span class="type">int</span> num = <span class="number">10</span>;</span><br><span class="line"><span class="comment">//定义了一个普通char类型变量text，他的值为a.对应上图就是0x03内存块中存储的内容</span></span><br><span class="line"><span class="type">char</span> text =<span class="string">&#x27;a&#x27;</span>;</span><br><span class="line"></span><br><span class="line"><span class="comment">//定义了一个int类型指针变量，他的值为num的地址0x01.对应上图就是0x04内存块中存储的内容</span></span><br><span class="line"><span class="type">int</span>* p1 = &amp;num ;</span><br><span class="line"><span class="comment">//定义了一个char类型指针变量，他的值为text的地址0x03.对应上图就是0x05内存块中存储的内容</span></span><br><span class="line"><span class="type">char</span>* p2 = &amp;text;</span><br></pre></td></tr></table></figure>

<h2 id="指针类型"><a href="#指针类型" class="headerlink" title="指针类型"></a>指针类型</h2><figure class="highlight plaintext"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br></pre></td><td class="code"><pre><span class="line">1、在定义指针的时候，前面的类型就是指针类型。如：</span><br><span class="line">int num = 10;</span><br><span class="line">int * p1 = &amp;num; //int 就是指针p1的类型。</span><br><span class="line"></span><br><span class="line">2、根据指针类型的不同，name指针的步长就不同。步长根据类型来判定</span><br><span class="line">char * 类型指针，步长是1个字节</span><br><span class="line">int * 类型指针，步长是4个字节</span><br><span class="line">double * 类型指针，步长是8个字节</span><br><span class="line"></span><br><span class="line">3、当解引用的时候，指针类型决定了编译器从首地址开始取多少字节。</span><br><span class="line"></span><br><span class="line">4、任何类型转换为无类型指针的时候，不需要强制转换。</span><br></pre></td></tr></table></figure>



<h2 id="运算"><a href="#运算" class="headerlink" title="运算"></a>运算</h2></article><div class="post-copyright"><div class="post-copyright__author"><span class="post-copyright-meta"><i class="fas fa-circle-user fa-fw"></i>文章作者: </span><span class="post-copyright-info"><a href="https://houyudong1989.gitee.io/blog">侯玉东</a></span></div><div class="post-copyright__type"><span class="post-copyright-meta"><i class="fas fa-square-arrow-up-right fa-fw"></i>文章链接: </span><span class="post-copyright-info"><a href="https://houyudong1989.gitee.io/blog/2024/05/06/c++/4%E3%80%81%E6%8C%87%E9%92%88%E5%92%8C%E5%87%BD%E6%95%B0%E6%8C%87%E9%92%88/">https://houyudong1989.gitee.io/blog/2024/05/06/c++/4%E3%80%81%E6%8C%87%E9%92%88%E5%92%8C%E5%87%BD%E6%95%B0%E6%8C%87%E9%92%88/</a></span></div><div class="post-copyright__notice"><span class="post-copyright-meta"><i class="fas fa-circle-exclamation fa-fw"></i>版权声明: </span><span class="post-copyright-info">本博客所有文章除特别声明外，均采用 <a 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id="card-toc"><div class="item-headline"><i class="fas fa-stream"></i><span>目录</span><span class="toc-percentage"></span></div><div class="toc-content"><ol class="toc"><li class="toc-item toc-level-1"><a class="toc-link" href="#%E6%8C%87%E9%92%88"><span class="toc-number">1.</span> <span class="toc-text">指针</span></a><ol class="toc-child"><li class="toc-item toc-level-2"><a class="toc-link" href="#%E6%8C%87%E9%92%88%E5%8F%98%E9%87%8F"><span class="toc-number">1.1.</span> <span class="toc-text">指针变量</span></a></li><li class="toc-item toc-level-2"><a class="toc-link" href="#%E6%8C%87%E9%92%88-%E6%93%8D%E4%BD%9C%E7%AC%A6"><span class="toc-number">1.2.</span> <span class="toc-text">指针 操作符</span></a></li><li class="toc-item toc-level-2"><a class="toc-link" href="#%E6%8C%87%E9%92%88%E5%A3%B0%E6%98%8E"><span class="toc-number">1.3.</span> <span class="toc-text">指针声明</span></a><ol class="toc-child"><li class="toc-item toc-level-3"><a class="toc-link" href="#%E9%87%8E%E6%8C%87%E9%92%88"><span class="toc-number">1.3.1.</span> <span class="toc-text">野指针</span></a></li><li class="toc-item toc-level-3"><a class="toc-link" href="#%E7%A9%BA%E6%8C%87%E9%92%88"><span class="toc-number">1.3.2.</span> <span class="toc-text">空指针</span></a></li></ol></li><li class="toc-item toc-level-2"><a class="toc-link" href="#%E6%8C%87%E9%92%88%E7%B1%BB%E5%9E%8B"><span class="toc-number">1.4.</span> <span class="toc-text">指针类型</span></a></li><li class="toc-item toc-level-2"><a class="toc-link" href="#%E8%BF%90%E7%AE%97"><span class="toc-number">1.5.</span> <span class="toc-text">运算</span></a></li></ol></li></ol></div></div><div class="card-widget card-recent-post"><div class="item-headline"><i class="fas fa-history"></i><span>最新文章</span></div><div class="aside-list"><div class="aside-list-item"><a class="thumbnail" href="/blog/2024/05/06/c++/5%E3%80%81%E5%AD%97%E7%AC%A6%E5%92%8C%E5%AD%97%E7%AC%A6%E4%B8%B2/" title="字符和字符串"><img src="/blog/img/library1.jpeg" 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